1. Field of the Invention
The present invention relates to improvements in a method for locking to and drawing out of a hook groove, which is provided in a housing, a plurality of lead wires which extend out from a circuit board of a cooling fan unit.
2. Description of the Related Art
A cooling fan unit used for cooling an electronic device includes an impeller having a plurality of blades, a motor for rotating the impeller, a circuit board mounting thereon a driver circuit for the motor, and a housing for fixing thereto the motor and the circuit board as well as accommodating therein the impeller. Connected to the circuit board are a plurality of (at least three) lead wires used for power supply and control, and there is attached, at ends of the lead wires, a connector for connection with an electronic device.
In accordance with a type, size, shape and the like of the cooling fan unit, there are various structures adopted for drawing the lead wires of the cooling fan unit out of the circuit board through the housing. There is a simple structure for a relatively small cooling fan unit in which a hook groove for locking the lead wires thereto is formed in an outer wall portion of the housing in a direction of drawing out the lead wires. Described below are examples of such a structure for drawing out lead wires in a conventional cooling fan unit.
FIGS. 8A and 8B are views of a structure for drawing out lead wires in a conventional cooling fan unit. FIG. 8A is a bottom view of the cooling fan unit seen from a side of a base portion in a direction of a central axis, while FIG. 8B is a partially enlarged cross sectional view of an outer wall portion of a housing of the cooling fan unit as seen from a direction of drawing out the lead wires. It is noted that an impeller is not illustrated in FIG. 8A.
A housing 1 of the cooling fan unit includes an outer wall 11, a base 12, and four joining portions 13 which connect the outer wall portion 11 and the base 12 with each other. The base 12 has a substantially cylindrical shape and accommodates therein a motor (not shown) and a circuit board 5. The circuit board 5 is partially exposed at a cutout 121 provided in the base 12. Lead wires 6 are soldered to a lead wire connection portion (including solder lands) which is provided at an area where the circuit board 5 is exposed. The lead wires 6 are attached at other ends thereof to a connector 7 which is used for connection with an electronic device.
There is formed a hook groove 110 in the outer wall 11 of the housing 1 in the direction of drawing out the lead wires. The hook groove 110 includes a lead wire through path 111 and a lead wire guide 112. The lead wires 6 are inserted sequentially one by one starting with a rightmost wire of FIG. 8A into the lead wire through path 111 and are accommodated in the lead wire guide 112.
There is another example of the structure for drawing out lead wires of the conventional cooling fan unit, in which there is provided a rib for guiding and accommodating the lead wires 6 from the connection portion of the circuit board 5 with respect to the lead wires 6 to the outer wall 11 of the housing 1. Further, there is a structure in which one of the joining portions 13 is formed to be wide to function also as a rib for accommodating the lead wires. However, these structures respectively have a drawback such that the wide rib for guiding the lead wires 6 counteracts airflow generated by rotation of the impeller. In order to overcome such a drawback, the conventional example shown in FIG. 8A adopts a structure in which there is provided no guide rib so that the lead wires 6 are exposed to airflow.
When the conventional cooling fan unit shown in FIGS. 8A and 8B is incorporated in an electronic device, one of the lead wires 6 aligned closest to the lead wire through path 111 (the leftmost lead wire in FIGS. 8A and 8B) is likely to be disengaged from the lead wire through path 111 depending on a way of drawing around the lead wires 6 within the electronic device. The lead wire 6 disengaged from the lead wire through path 111 (that is, the hook groove 110) may widely swing due to the airflow, which will cause noise. Further, the disengaged lead wire 6 may be brought into contact with another component within the electronic device to damage coating thereof or to be thermally deteriorated.
Disengagement of one of the lead wires 6 from the hook groove 110 can be prevented by applying an adhesive agent or an adhesive tape so as to block an opening of the lead wire through path 111. However, it is desirable not to perform such work which requires an additional cost and manufacturing step.